[DGD]string reference/swapout problems

[Marc Spoorendonk]

On Fri, 5 Mar 1999, Felix A. Croes wrote:

> Marc Spoorendonk <marc at freud.et.tudelft.nl> wrote:
> 
> >[...]
> > I have attempted to code a really simple piece of code: A global errstr
> > string which can be shown to the coder when a function returns an error
> > state.
> >
> > What I want is:
> > void set_errstr(string error_string);	// stores a string into the driver
> > string get_errstr();			// retrieves the string
> >
> > Ofcourse this can be done with a str_new() but i thought that it should be
> > possible to store just a pointer to the string in the driver. (see the
> > paste of the source code) This works fine but when i force a swapout, the
> > string gets swapped out and we get stuck with a string pointer which
> > points into unknown space.
> >
> > My question is: Is there a way to prevent the string from being swapped
> > out?
> 
> You can prevent swapping altogether in the config file by setting both
> swap_fragment and static_chunk to 0, and masking swapout() in the
> auto object.  That is the only way to prevent LPC datatypes, such as
> strings, from being swapped out.

That has ofcourse nothing to do with my problem. Swapping is cool, I don't
want to shut it off. The question is: Can i store a string in the driver
by reference. Or do i always need to copy it due to swapout problems
otherwise? 

> 
> 
> > And the general question: When do i need to str_ref() or str_del() when
> > using strings in kfuns? 
> 
> str_ref(): whenever a pointer starts to point to a string.
> str_del(): whenever a pointer that points to a string is assigned a
>            new value, or becomes invalid.  In particular, if a
> 	   string is popped from the runtime stack, the pointer on
> 	   the stack becomes invalid and therefore str_del() has to
> 	   be used.

Ah, Thanx for this info.
> 
> Regards,
> Dworkin
> 
> List config page:  http://list.imaginary.com/mailman/listinfo/dgd
> 

Regards,
Marc

--
Marc Spoorendonk
Department of Electrical Engineering
Delft University of Technology

e-mail			: Marc at freud.et.tudelft.nl
mud			: telnet://freud.et.tudelft.nl:8888
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